The present invention relates to an improvement of an operating mechanism for a circuit breaker.
A conventional operating mechanism for a circuit breaker is shown in FIG. 1 wherein the reference numeral (1) designates an operating handle; (2) designates a spring one end of which is connected through a pin (14) to the operating handle (1); and the other end of the operating handle (1) is connected to fulcrum (10) formed on the box (16). The other end of the spring (2) is connected to a connecting shaft (6) of the lever (8) and the lever (13). The lever (8) is connected to a movable part which is rotatably connected through an arm (15) at one end to a stationary shaft (9) including the movable contact (3). The movable contact (3) faces a stationary contact (4) to form a pair of switch electrodes. The other end of the lever (13) is connected to a hook (7) which is rotatably connected through the shaft (5) to the stationary shaft (11). The end of the hook (7) is fitted to a lock (12) which is actuated by a tripping mechanism (not shown). FIG. 1 shows the reset opening stated.
The operation of the embodiment will be illustrated.
When the operating lever (1) is turned in the clockwise direction, the pin (13) is rotated around the center of the fulcrum (10) whereby the spring (2) connected to the shaft (6) is gradually actuated. The force applied to the spring (2) is the force for rotating clockwise the lever (13) around the center of the shaft (5) until it reaches from A to B. When the movable contact (3) is in the opening state, by the movement of the lever (8), the movement of the contact is controlled. When it moves over B, the lever (13) is rotated in the counter-clockwise direction by the force actuated by the spring (2). As a result, the shaft (6) swings to the right direction whereby the lever (8) turns in the clockwise direction so as to push down the shaft (15) and the movable contact (3) is closed.
Thus, when the operating lever (1) is turned to the left direction from the closed state, the lever (13) is turned in the clockwise direction by the reverse movement, whereby the movable contact (3) is opened to be in the state shown in FIG. 1 and the contact of the movable contact is released.
On the other hand, when a lock (12) is turned to the left by the movement of the tripping mechanism (not shown) to release the interlocking with the hook (7), the hook (7) is freely turned to the clockwise direction around the ceter of the shaft (11) even though it is in the closed state or the closing state whereby the shaft (6) is raised by the force of the spring (2) so that the movable contact (3) moves into in the opening state.
The operating mechanism of the conventional circuit breaker has such structure. Therefore, the force of the spring (2) is not directly transmitted to the movable contact, but is applied through the toggle formed by the levers (13) and (8). The output is obliged to utilize a part of the force of the spring (2). Therefore, it is necessary that the spring (2) is undesirably larger. Thus, it is necessary that the structure of the shaft or the lever should be durable to a stress greater than the force required for closing or opening the contacts of the circuit breaker. Thus, it is difficult to form a compact structure economically.
On the other hand, the lever is operated at special angles and the positions of the levers (8) and (13), the operating lever (1), the hook (7) and the spring (2) are superposed three dimensionally whereby the supports, the structures and the arrangements are complicated. Usually, only the hook (7) has one arm and the spring (2), the lever (8), the lever (13) and the operating lever (1) respectively have two arms. The number of the parts is large and high technical skill and long experimentation are required in its assembly, disadvantageously. Moreover, when the operating lever (1) is turned over the line B in the closing operation, the operating lever itself is quickly turned to right by the force of the spring (2). When the lock (12) is released, the operating lever itself is quickly shifted to the free position whereby it may cause damage to an operator. The trip state caused by the releasing operation of the lock (12) can be given at the position being different from the opening position of the operating lever (2). Therefore, it is necessary to provide a reset position for interlocking the lock (12) with the hook (7) in order to shift it from the trip state to the closing state. Moreover, it is necessary to apply by an operator, the operating force being substantially the same as the force required for closing it at the its opening operation or the resetting operation to actuate the spring (2).